Lewis Maurice Joachim was born in Melbourne on 18 December 1897 to Joseph and Charlotte Joachim (née Cohen). Before the First World War, Joachim served five years as a lieutenant with the cadet forces, and then worked as a salesman.

On 18 January 1916, at the age of 19, Joachim enlisted in the Australian Imperial Force and was allotted to the 17th Infantry Battalion with the rank of acting sergeant. He embarked from Sydney on 13 April 1916 aboard HMAT Ceramic. Joachim arrived in Étaples on 11 August 1916 and soon after he was reassigned to the newly-formed 53rd Battalion. The battalion spent the winter of 1916–17 rotating in and out of trenches in the Somme Valley. Joachim was hospitalised on 16 September 1917 with a sprained ankle, returning to his unit on 14 November 1917. He was detached to the 14th Field Company Engineers from 19 November 1917 for a short time before rejoining the 53rd Battalion for the remainder of the war.

From late May 1916 until the end of 1918 Joachim wrote a number of letters to his parents. In these letters, Joachim discusses his training, homesickness, his impatience to leave for France and his time spent in hospital after injury.

Joachim returned to Australian aboard HMAT Ulysses in January 1919. In 1921 he married Lurline Cohen. The couple went on to have three children, one of whom, Ronald, served in the Second World War. Lewis Joachim died on 2 July 1939, aged 42.